Cutting teeth for circular saw blades

ABSTRACT

The invention disclosed pertains to improved raker and low teeth for use in circular saw blades. Each raker tooth includes a leading face and a top portion. The leading face comprises a first and second planar surface wherein the second surface extends at a negative angle from the first surface and to the top that consists of five facets in which two pairs of facets lie in planes offset at a first and second angles from the plane of a first center facet. Each low tooth also includes a leading face and top portion. However, the leading face includes a first planar surface and a second portion consisting of five facets each of which extends from the first surface to the top portion at a negative angle of inclination, and two pairs of facets lie in planes offset at first and second angles from a first center facet.

FIELD OF THE INVENTION

The present invention relates to teeth for use in circular saw bladesand, in particular, to raker and low teeth inserts which arealternatively positioned about the periphery of a circular saw blade.

BACKGROUND OF THE INVENTION

The use of inserts made of carbide are generally well known in the art.Various geometries have been proposed for such inserts which, for themost part, were to overcome problems associated with wear ordeterioration. Various spherical or cylindrical geometries have beenproposed such as U.S. Pat. Nos. 2,675,603, 3,537,491, 3,788,182 and4,012,820. Other improved metal cutting geometries have been proposed inU.S. Pat. Nos. 3,576,061 and 3,576,200. Most importantly, the geometriesproposed in U.S. Pat. Nos. 3,576,061 and 3,576,200 were shown to haveincreased the life of the blade as well as improved its metal cuttingcapability.

Generally, the geometry of U.S. Pat. No. 3,576,061 comprises a hightooth which has an outer central cutting edge at the top surface whichintersects a negatively raked front face which is used to first remove achip from the center of the kerf. Each high tooth is followed by a lowtooth having a front face with a negative rake and two plane shearingfaces that angle backwardly and flare laterally and outwardly fromeither side of the front face to remove two chips, one from each side ofthe kerf flanking the center chip. U.S. Pat. No. 3,576,200 provides ageometry for removing five chips from the kerf rather than three. Thegeometry taught therein comprises a high tooth having a central outeredge and two lateral cutting edges to remove three chips followed by alow tooth which includes two lateral cutting edges that are positionedbetween the outer and lateral cutting edges of the high tooth to providetwo chips. The geometries taught in U.S. Pat. Nos. 3,576,061 and3,576,200 provide circular saw blades which exhibit better metal cuttingproperties and longer life.

A suggested improvement over the triple-chip cutting teeth is set forthin U.S. Pat. No. 4,012,820 in which the working surface of the high andlow teeth is arcuate rather than planar, but includes beveled top sidessimilar to U.S. Pat. No. 3,576,061. The principal advantage of theproposed design resides in the relative ease of grinding the arcuateworking surface compared to three planar surfaces of the prior art.

Although it has been found that generally arcuate surfaces can beprepared with greater ease than a number of offset planar surfaces,planar working surfaces have been found to have better metal cuttingcharacteristics and longer life than arcuate working surfaces.Accordingly, it is an object of the present invention to provide cuttingteeth having planar working surfaces which have better metal cuttingcharacteristics than the teeth disclosed in U.S. Pat. Nos. 3,576,061 and3,576,200.

SUMMARY OF THE INVENTION

The present invention provides a raker tooth and low tooth, each ofwhich preferably are manufactured from a carbide material, such astungsten carbide, as an insert for use in circular saw blades. As inconventional saw blades, the raker and low teeth are alternatinglypositioned about the periphery of the blade typically by brazing theminto corresponding pockets within the teeth of the saw blade. The teethof the present invention are improvements over those taught anddisclosed in U.S. Pat. Nos. 3,576,061 and 4,012,820.

Generally, the raker teeth of the present invention comprise a leadingface and top portion. The leading face includes a first planar surfaceand a second planar surface which extends from the first planar surfaceto the top portion at a negative angle of inclination. The top portionof the raker teeth consists of five facets which are angularly offsetfrom each other to define cutting edges therebetween.

The low teeth, on the other hand, provide a leading face which includesa first planar surface portion and a second portion which consists offive facets all of which are inclined at a negative angle from the planeof the first surface. Each of the five facets of the second portion areangularly offset from each other to define cutting edges which extendfrom the first planar surface to the top of the tooth. The top portionof the low tooth preferably lies in a plane which intersects the planeof the first planar surface at an angle slightly less than normal.

Compared with the conventional "triple-cut" teeth, a blade having theraker and low teeth of the present invention was found to havesubstantially improved performance, particularly in the area of wear.Other advantages of the present invention will become apparent from aperusal of the following detailed description of the presently preferredembodiment of the invention taken together with the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a partial side view of a saw blade showing raker and low teethalternatingly positioned about the periphery of the blade;

FIG. 2 is a perspective view of the raker tooth of the presentinvention;

FIG. 3 is a front elevation of the raker tooth;

FIG. 4 is a top view of the raker tooth;

FIG. 5 is a perspective view of the low tooth of the present invention;

FIG. 6 is a front elevation of the low tooth; and

FIG. 7 is a top view of the low tooth.

PRESENTLY PREFERRED EMBODIMENT

Referring to FIG. 1, the outer peripheral portion of a conventional sawblade 10 is shown with teeth 11 uniformly distributed around the bladedisc. Each tooth 11 includes a pocket 12 into which a cutting toothinsert is adapted to be positioned. As shown, raker tooth A and lowtooth B of the present invention are alternatingly positioned on teeth11. Preferably, raker teeth A and low teeth B are made from conventionalcarbide material, such as tungsten carbide, typically used in themanufacture of carbide cutting teeth.

With reference to FIGS. 2-4, raker tooth A comprises a leading surface14 which includes a first planar surface 16 and a second planar surface17 which extends from the first planar surface to the top portion 18.First planar surface 16 is adapted to lie in a plane which is parallelto a radial plane R (FIG. 1) of the blade. The second planar surface 17is inclined at a negative angle φ to the radial plane R of the blade.[Negative angle means throughout an inclination away from the directionof rotation of the saw blade or the leading edge of the tooth].Preferably, negative angle φ is about 15°. However, variations of withinabout ± 10° of the preferred angle φ can be used advantageously withcertain types of metals. However, it has been found that the preferredangle φ of 15° provides the best performance for a broad range ofmaterials.

Top 18 of each raker tooth consists of a first center facet 19 whichlies in a plane substantially normal to the plane of the first planarsurface 16. Positioned on either side of first facet 19 are second facet22 and third facet 23, respectively, each of which lies in a planeangularly offset from the plane of the first facet by a first angle φ₁which defines first edges 21 therebetween. First angle φ₁ is betweenabout 10° and 20° and preferably about 15°. Positioned adjacent to eachsecond facet 22 and third facet 23 are fourth facet 24 and fifth facet25, respectively. Each of the fourth and fifth facets lies in a planewhich is angularly offset from the plane of first facet 19 by a secondangle φ₂ which defines second edges 26. Second angle φ₂ is between about30° and 45° and preferably about 40°. The fourth facet 24 and fifthfacet 25 each join the respective sides 28 and 29 to form third edges27.

Sides 28 and 29 of raker tooth A have radial clearance angle α ofbetween 1° and 3° and preferably 2° to prevent the saw blade frombinding in the material it is cutting. In utilizing raker tooth A with aconventional saw blade 10, it is preferable to bevel trailing edges 31of tooth 11 as shown in FIGS. 1 and 2. Bevels 31 permit the facets oftop portion 18 to extend slightly above the surface of teeth 11 toprotect teeth 11 from wear or deterioration during cutting.

The low teeth B of the present invention comprise a leading face 33 andtop portion 34. The leading face 33 includes a first planar surface 36and a second portion 37. First planar surface 36 is preferably adaptedto lie in radial plane R of blade 10. Second portion 37, however, isinclined at a negative angle from first planar surface 36 to top portion34.

Second portion 37 consists of a first center facet 41 inclined atnegative angle φ, where φ is between about 5° and 25° and preferablyabout 15°. Positioned adjacent to center facet 41 is second facet 42 andthird facet 43. Second facet 42 and third facet 43 each lie in a planewhich is angularly offset from the plane of first facet 41 by firstangle φ₁ which defines edges 47 therebetween. First angle φ₁ is betweenabout 5° and 25° and preferably about 15°. Positioned adjacent to secondfacet 42 is fourth facet 44 and positioned adjacent to third facet 43 isfifth facet 45. Each of the fourth and fifth facets 44 and 45 lie in aplane which is angularly offset from the plane of first facet 41 by asecond angle φ₂ which defines second edges 48. Second angle φ₂ isbetween about 15° and 45° and preferably about 30°. The fourth and fifthfacets 44 and 45 adjoin side 51 and 52, respectively to define thirdedges 54. Preferably, the width W_(b) of first planar surface 36 isslightly greater than the width W_(bb) of the back of insert B and thesame as the width of raker tooth A beween edges 27. As with raker toothA, the sides of low tooth B have a radial clearance angle β which isbetween 1° and 3° and preferably 2°.

As an example of the improved performance obtainable with the presentinvention, a 32" diameter saw having 60 teeth, comprising 30 raker teethA and 30 low teeth B was used to cut steel bars. The bars were 6" roundT-1 high carbon steel (28.5 in.² /cut). The blade was operated at 56 RPM(dry cut with air jets) with a 10" travel/min. and was checked every tencuts. The initial cutting time was 40 seconds which increased to 45seconds. The blade cut 11,538 in.² of steel compared to 6,280 in.² withtypical triple-cut geometries.

It is believed that the improved performance is obtained because theinserts of the present invention remove five small chips. Because thesechips are smaller, they are now more easily removed and do not get stuckbetween the tip of the insert and material being cut. Accordingly, thewear is more uniform.

Additionally, it has been found that with the inserts of the presentinvention there appears to be better distribution of pressure betweenthe insert and the material as shown by lower power requirements ascompared to prior art inserts.

The blade ran cool to the touch and wore uniformly. At the end of thetest, only sharpening was required. Accordingly, a substantialimprovement was achieved using the teeth of the present invention.

While a presently preferred embodiment of the invention has been shownand described with particularity, it may be otherwise within the scopeof the appended claims.

We claim:
 1. A low cutting tooth for use in combination with a rakertooth in circular saw blades comprising a leading face and a top, saidleading face including a first planar surface and a second portionconsisting of a first center facet inclined at a negative angle from thefirst planar surface to the top, second and third facet, each positionedadjacent to the first facet and lying in a plane angularly offset fromthe plane of first facet by a first angle to define first cutting edges,and fourth and fifth facets positioned adjacent said second and thirdfacets respectively, each lying in a plane angularly offset from theplane of the first facet by second angle to define second cutting edges,said fourth and fifth facets defining third cutting edges with theassociated side of the tooth, and each of said sides has a radialclearance angle β.
 2. A low tooth as set forth in claim 1 wherein saidnegative angle is between about 5° and 25°, said first angle is betweenabout 5° and 25°, said second angle is between about 15° and 45°, and βis between 1° and 3°.
 3. A low tooth as set forth in claim 2 whereinsaid negative angle is 15°, said first angle is 15°, said second angleis 30°, and β is 2°.
 4. A low tooth as set forth in claim 2 wherein saidraker tooth for use in combination therewith comprises a leading faceand a top, said leading face including a first planar surface and secondplanar surface extending from said first planar surface to said top andlying in plane inclined at a negative angle from the plane of the firstplanar surface; and said top consisting of a first center facet lying ina plane substantially normal to the plane of first planar surface;second and third facets, each positioned adjacent said first facet andlying in a plane angularly offset from the plane of the first facet by afirst angle to define first cutting edges; fourth and fifth facets, saidfourth facet being positioned adjacent said second facet and said fifthfacet being positioned adjacent said third facet, each of said fourthand fifth facets lying in a plane angularly offset from the plane of thefirst facet by a second angle to define second cutting edges, saidfourth and fifth facets defining third cutting edges with the associatedside of said tooth, and each of said sides has a radial clearance angleα .